Arctic Ocean hits irreversible chemical tipping point as ice loss drains nitrate

Two decades of data show sun-driven nutrient loss after sea ice retreats triggers benthic denitrification on shallow Arctic shelves, causing irreversible nitrate depletion and pushing the Arctic Ocean past a tipping point around 2009. The nitrate famine is already reshaping the food web from plankton to fish, seabirds, and marine mammals, with potential impacts on North Atlantic fisheries and broader marine ecosystems, and researchers say the system is unlikely to revert to its previous state without major changes in ice cover.